Recent active phase of symbiotic system V694 Mon (MWC 560)

V.P. Goranskij, V.T. Doroshenko (SAI, Moscow University); E.A. Barsukova, S.N. Fabrika, O.N. Sholukhova, A.F. Valeev (Special Astrophysical Observatory, Russia)

Published in Astronomer's Telegram No. 3149

V694 Mon is a known symbiotic variable star with a high-velocity jet manifesting itself in broad blue-shifted absorption components of Balmer emission lines. The star showed rapid brightness variations in the scale of minutes with the amplitude up to 0.4 mag in the V band, and the large outburst in 1990. It also slows variations with the period of 1930 days (Doroshenko et al., IBVS 3824, 1993) and with the mean amplitude of 0.75 mag in the B band, the epoch of maximum is JD 2438435. The recent brightening has happened after the faint stage continued between January 2008 and December 2009. U,B,V, and Cousins R magnitudes measured using SAO 1 m telescope and SAI Crimean Station 60 cm telescope equipped with CCD photometers are the following:
2009 Oct 22.12 UT (11.037, 11.196, 10.865, 9.859);
2010 Nov 4.12 UT (10.471, 10.563, 10.329, 9.654);
2010 Dec 4.00 UT (9.805, 9.995, 9.779, 9.201);
2010 Dec 24.99 UT (9.490, 9.936, 9.616, 9.041);
2011 Feb 1.85 UT (10.123, 10.200, 9.897, 9.188).
The recent outburst reached the peak brightness in the end of December 2010, that is within the phase range of 0.86-0.89 calculated with ephemeris given above. Then the star was only 0.4 mag fainter than in the strongest 1990 event, so the recent event is the second in power. The active state may continue in 2011.

Figure 1. The light curve showing all the historical observations in the B band. The systematic brightening trend was deleted. The last observations are given in the circles.

On 2011 January 3.046 UT, we have taken the spectrum of V694 Mon using the Russian 6-m telescope BTA equipped with the SCORPIO spectral camera. The spectrum has a resolution of ~13 A and covers the region 3626 - 7876 A. Stationary emission is seen in H-alpha, H-beta and H-gamma lines at the radial velocity of +60 km/s. Equivalent widths of these lines are -86, -11 and -2.5 A, correspondingly. There are many FeII emissions in the spectrum. The absorption components of Balmer lines and HeI 5875.6 A line are extended towards the blue side to the velocity of -4200 km/s. The deepest absorption is seen at the velocity of -3100 km/s with depths of 0.36 and 0.46 relative to continuum level in H-alpha and H-beta. Whereas H-gamma line and higher Balmer lines have double absorption profile with components at -700 and -3200 km/s. HeI 5875.6 A absorption is also double with the components at -350 and -3300 km/s. Absorption components of H-alpha, H-beta and H-gamma have equivalent widths 27, 17 and 10 A, correspondingly, and absorption component of HeI line has EW = 5 A. The M-type star spectrum is observed well above 6000 A, but the molecular TiO absorption band heads may be identified at lower wavelength. The spectrum confirms high-level activity in V694 Mon.

Figure 2. The medium resolution spectrum of V694 Mon taken with the Russian 6-m telescope BTA and SCORPIO spectral camera.

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